Method of forming a conveyor chain link having knuckles formed integrally with edge

ABSTRACT

A flat top metal conveyor chain link is formed with the curled knuckles of one edge extending a short distance into the flat body of the link. The remainder of the one edge outwardly of the knuckles is swaged to a rounded form corresponding to the portion of the knuckles integral with the link body. The opposite edge is beveled or undercut to allow adjacent connected links to overlap slightly and interfit more closely. The cold working of the metal by swaging produces localized increases in strength allowing relative changes in the widths of the knuckles on respectively opposite edges of the link, whereby an increase in the ultimate and fatigue strengths of the link may be attained.

United States Patent 1 ,2

Mueller Dec. 19, 1972 54] METHOD OF FORMING A CONVEYOR 2,852,129 9/1958 Conner ..l98/189 CHAIN LINK HAVING KNUCKLES 2,911,091 1151959 lmse 3,144,124 8 1964 Hein... FORMED INTEGRALLY WITH EDGE 3,442,076 5/1969 Marlo-m [72] Inventor: Clair W. Mueller, Wauwatosa, Wis. 3,514,941 6/1970 Mueller ..59/35 [73] Ass1gnee: Rex Chainbelt Inc., Milwaukee, Wis. Primary Examiner Lowe Larson [22] Filed: June 21, 1971 Assistant Examiner-Gene P. Crosby 1 pp 155 317 Attorney-Ernst William Schultz Related U.S. Application Data [57] ABSTRACT A flat top metal conveyor chain link is formed with 62 D N t 1 :22?" of Set 0 May 1969 the curled knuckles of one edge extending a short distance into the flat body of the link. The remainder [52] U.S. c1. ..s9/3s, 59/91, 198/189 the edge madly knuckles a rounded form corresponding to the port1on of the [51] Int. Cl. ..B21l 11/00 [58] Field of Search 59/35 6 l2 l3 14 15 90 I knuckles integral w1th the lmk body. The opposite "5 1 4 edge is beveled or undercut to allow ad acent conr 1 nected links to overlap slightly and interfit more close- 1y. The cold working of the metal by swaging produces [56] References cued localized increases in strength allowing relative UNITED STATES PATENTS changes in the widths of the knuckles on respectively oppos1te edges of the lmk, whereby an increase 1n the 2 34190; Pruden ..72/379 ultimate and fatigue strengths of the link may be at- 10 194 ..l98/189 taine 2,569,636 10/1951 lmse ..198/l89 2,660,292 11/1953 Cheesman ..198/l89 6 Claims, 10 Drawing. Figures PATENTED DEC 19 1972 SHEET 2 BF 3 METHOD OF FORMING A CONVEYOR CHAIN LINK HAVING KNUCKLES FORMED INTEGRALLY WITH EDGE CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of application, Ser. No. 827,677 filed May 26, 1969, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to the art of flat top conveyor chains wherein adjacent metal links having interfitting knuckles are pin-connected to form a chain with a contiguous flat conveying surface, adapted to be sprocket-driven and operated over a pair of longitudinally extending, spaced wear strips. More particularly, this invention relates to improvements in links of such chains formed from sheet metal and in the method of forming them.

2. Description of the Prior Art Flat top conveyor chains are known in the art and, of the various types in common use, the most common is the type in which the individual links have a flat body portion of generally rectangular shape and cylindrical knuckles extending from opposite edges of the flat body. The knuckles are adapted to interfit with the knuckles of adjacent links and to be interconnected with hinge pins to form an endless chain. Links of a flat top conveyor chain are generally formed either of sheet metal or of plastic or a similar synthetic material. The former are made by stamping flat blanks from sheet metal, each blank having a central body portion which forms the flat conveying or article carrying portion of the link, and tongue portions extending from opposite edges of the body which are curled in a forming operation to form the interfitting pin receiving knuckles. Plastic links are simply molded to the desired form which conforms, in general, to the shape of metal links.

The chain is adapted to be driven by a sprocket through engagement of the interconnected link knuckles by the sprocket teeth. In operation, the chain is supported and guided by a pair of spaced wear strips. The wear strips engage the flat undersides of the body portions of the links outwardly of the knuckles so that the upper run of the chain is supported along its entire length. The wear strips are spaced apart just sufficiently to allow the pin-connected knuckles to travel therebetween and to thereby guide the chain along its path of travel.

Industry standards dictate the lateral spacing between wear strips and it follows, therefore, that the lateral distance occupied by the link knuckles is limited by those standards. The strength or load capacity of this type of flat top conveyor chain is dependent on the strength of the knuckles which generally include a pair of laterally spaced knuckles extending from one edge of the body of the link, and a centrally disposed knuckle extending from the opposite edge and adapted to fit between the spaced knuckles of the adjacent link.

A balanced, maximum strength chain design requires that the strength of the central knuckle equal the combined strengths of the spaced knuckles. Thus, given a standard wear strip spacing, in a prior art chain link formed from a sheet metal stamping the central knuckle will have a width equal to approximately onehalf that spacing and the spaced knuckles will each have a width of approximately one-fourth the spacing.

- In operation and despite attempts to balance the strengths of the spaced knuckles and the interfitting central knuckle, it has been shown that prior art metal chain links fail most generally with a fatigue or an ultimate strength failure of the spaced knuckles. These failures may be attributed to an unbalanced loading of the link wherein one spaced knuckle is more heavily stressed through chain tension than the other, or to fatigue cracking as a result of undesirable stress concentrations produced in the link forming operation. The failure of a spaced knuckle will usually occur in the portion extending from and immediately adjacent to the flat body portion of the link and such failure is characterized by a raising or lifting of the knuckle relative to the body portion.

In prior art chains with molded plastic links, a balanced, high strength design has been attainable, without regard to balancing the knuckle widths, by forming reinforcing ribs integrally with the knuckles andthe undersides of the links inthe molding process. The addition of any similar type of reinforcing to metal links, as is shown for example in U.S. Pat. No. 2,564,533, has been found to be costly and impractical. Thus, the strength of chain having metal links has been limited by the required balanced design described previously.

In prior art flat top conveyor chains, a primary consideration has been to minimize the spacing or gap between adjacent links. By minimizing or eliminating this gap a more nearly continuous flat conveying surface may be provided. It is known in the art to form molded plastic links such that opposing edges of adjacent links overlap slightly whereby the gaps therebetween may be eliminated, as is shown in U.S. Pat. No. 2,911,091. No suitable method has heretofore been found to so form the edges of links formed from sheet metal.

Several methods of decreasing the spacing or gap between metal flat top chain links are known in the art. One such method is disclosed in U.S. Pat. No. 3,514,941. However, this and other known methods can be used to decrease but not eliminate the longitudinal gap between interconnected metal links.

SUMMARY OF THE INVENTION The present invention discloses a method of forming flat top conveyor chain links of sheet metal in a manner wherein the strength of the chain is substantially increased by a cold working of the metal. Such cold working is simultaneously utilized to cooperatively form the opposite edges of each link such that the adjacent edges of the interconnected links overlap slightly to provide a continuous conveying surface.

The invention provides a method of substantially increasing the ultimate and fatigue strengths of stamped steel flat top conveyor chains without changing critical dimensions of the component links set by industry standards and without the addition of costly reinforcing structure to the links. By swaging one edge of the link to a rounded form and forming the spaced curled knuckles extending from that edge such that portions of the outside surfaces of the knuckles form continuations of the swaged edge, the work hardening of the edge,produced as a result of the swaging, provides an increase in the strength of the curled knuckles.

The increase in strength of the spaced knuckles allows the widths of the tongues from which they are formed to be decreased. correspondingly, the width of the central tongue of the opposite edge, from which the central knuckle is formed, may be increased. The net effect is a link having an overall knuckle width within the limits established by industry standards, yet having substantially increased ultimate and fatigue strengths.

Additionally, by forming portions of the knuckles of one edge integrally with that edge and by swaging a bevel on the underside of the opposite edge, the interconnected links may be made to interfit more closely; i.e. the longitudinal gap between adjacent links may be substantially eliminated.

The swaging of the edge of the link to correspond to and form. a continuation'of theisurfaces of the .spaced curled knuckles can be employed to provide a strength increase in links formed of low work hardenable steels. The strength increase is a result of the reinforcing provided by'the swaged rounded edge to that portion of the curled knuckle most susceptible to failure; i.e. the portion of the knuckle immediately adjacent the body of the link.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of several conveyor chain links of the present invention operatively interconnected.

FIG. 2 is an enlarged side view partly in section taken on line 2-2 of FIG. 1.

FIG. 3 is a bottom plan view of a stamped sheet metal blank from which a link of the present invention is formed. v I

FIG. 4 is an enlarged side view of the blank of FIG. 3 showing the preforming of the tongue ends.

.FIG. 5 is a plan view of the punch and die used in U- forming the links in accordance with the method of the present invention with the punch shown viewed from the underside.

FIG. 6 is an enlarged side elevation view of the U- fonning tooling in operative association with a link blank at an intermediate position of the downward stroke of the punch.

FIG. 7 is an enlarged side elevation view similar to FIG. 6 showing a fully U-formed blank with the punch at the bottom of its stroke.

FIG. 8 is a view similar to FIG. 7 showing a vertical section taken on the longitudinal centerline of the U- forming tooling and the blank.

FIG. 9 is an enlarged front elevation view of a fully formed link of the present invention.

FIG. 10 is a perspective view of the link shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing, FIGS. 1 and 2 show several links of a flat top conveyor chain of the present invention operatively interconnected. Each link 10 has a flat body portion 12 of a generally rectangular shape. A pair of spaced curled-knuckles 14 are formed integrally with the body portion 12. The knuckles 14 are generally cylindrical in cross section and curl downwardly from the leading edge 16 of the link and terminate adjacent the flat underside 18 of the link body suchthat the greater portion of the knuckles 14 lies thereunder. The spaced knuckles 14 are formed with aligned bores 15. A central knuckle 20 extends rearwardly, with respect to the direction of chain travel indicated by the arrow in FIG. 1, from the trailing edge 22. The central knuckle 20 iscurled so as to define a bore 21 therethrough similarly as the spaced knuckles 14, but lies substantially without the underside 18 of the link body 12.

The leading edge 16 of the link between the spaced knuckles 14 is offset inwardly so as to define an indented margin 24. The indented margin 24 provides the space necessary for the interfitting central knuckle 20 of an adjacent link 10 such that the bores 15 and 21 of respective adjacent links may be aligned for the receipt of a connecting pin 26. y

' Each link 10 is formed from a flat sheet metal blank 28, as shown in FIG. 3. The blank 28 is stamped from sheet metal stock, most commonly steel or stainless steel. The metal blank 28 includes the generally rectangular body portion 12 of the finished link 10. A pair of spaced tongues 30 extend from the leading edge 16 of the body portion 12 and a central tongue 32 extends from the trailing opposite edge 22 of the body portion. The leading edge 16 is provided with the indented margin 24 between the spaced tongues 30. 4

Before the blank 28 is stamped, the flat sheet metal stock is preferably knifed to form a bevel 23 defining a portion of the underside of the'trailing edge 22 and a bevel 25 similarly defining the edge of the indented margin 24 in the manner and for the purposes disclosed in US. Pat. No. 3,514,941. As also disclosed therein, the lateral edges of the tongues 30 and 32 may be swaged or coined after the blank 28 is stamped from the sheet metal stock. However, links of the present invention may be formed without swaging the lateral edges of the tongues as disclosed in the above identified application, and the bevels 23 and 25 may beformed in a subsequent manufacturing step as will be described below.

Referring to FIG. 4, the blank 28 is preferably preformed in a known manner to facilitate the subsequent curling operation. This preforming operation comprises pressing the blank 28 into a die with a punch such that the ends 31 of the tongues 30 and the end 33 of the tongue 32 are turned downwardly with respect to the upper surface of the blank to form the end portions of the curled knuckles 14 and 20, respectively.

The preformed blank 28 of FIG. 4 is then U-formed in the manner of the present invention. The U-forming imparts a precurl to portions of the tongues 30 and 32 adjacent the body portion 12 of the blank 28, and additionally provides a swaging of the leading edge 16 to a rounded form corresponding to the precurled portions of the spaced tongues 30. Simultaneously with the swaging of the leading'edge 16, the remainder of the trailing edge 22 is swaged outwardly of the knife-' formed bevels 23 to form therewith a continuous bevel along the underside of the edge 22.

FIG. 5 illustrates the U-forming tools and FIGS. 6 7 and 8 their operation. The preformed blank 28 is pressedinto a U-shaped die 38 with a punch 40. The die 38 and punch 40 are each preferably constructed of three separate parts compositely secured in their respective operative positions with appropriate tool holders (not shown).

The U-shaped die 38 comprises a centrally disposed precurling die 42 and a pair of swaging dies 44 cooperatively adjoined to opposite sides of the precurling die. The punch 40, in a like manner, includes a central precurling punch 46 and a pair of swaging punches 48 disposed on opposite sides of the precurling punch.

The preformed preformed blank 28 of FIG. 4 is placed inverted on the die 38 and is positioned and held in place through the U-forming operation by a set of locators depending downwardly from the precurling punch 46. A central locator 50 is adapted to fit within the indented margin 24 of the blank 28'and to be received in a guide hole 52 in the precurling die 42 as the punch 40 approaches the die 38 on the downward stroke. A pair of spaced locators 54 fit adjacent the opposite'edges. of the central tongue 32 and the knifeformed bevel 23 of the trailing edge 22 of the blank. The locators 54 are received in a corresponding pair of guide slots 56 in the precurling die 42.

The precurling punch 46 has a flat lower surface 58. With respect to the positioned blank 28 of FIG.'6, the leading edges 60 of the precurling punch outwardly of the central locator 50 are rounded and have radii of curvature substantially equal to those of the bores of the spaced curled knuckles 14 of the link 10. Likewise, the trailing edge 62 of the precurling punch between the spaced locators 54 is rounded to conform to the desired curvature of the bore 21 of the central curled knuckle 20. The lengths of the rounded leading edges 60 and the trailing edge 62 correspond respectively to the widths of the spaced tongues 30 and the'central tongue 32 of the blank 28.

The swaging punches 48 each have a flat surface portion 64 which lies coplanar with the lower surface 58 of the precurling punch 46. The trailing portion 66 of each swaging punch, however, is stepped or offset downwardly to define a beveled swaging surface 68.

The precurling die 42, as shown in FIG. 5, has a 3 generally U-shaped cross section. The bottom portion 70 of the die 42 has a flat continuous surface, except for the guide hole 52 and guide slots 56. The leading comer 72 of the precurling die is rounded in conformity to the outside surfaces of the spaced curled knuckles 14. The rounded comer 72 is divided by the guide hole 52 into two equal portions corresponding to the two leading edges 60 of the precurling punch 46. The trailing comer 74 of the precurling die is similarly rounded and has a length, between guide slots 56, equal to the length of the trailing edge 62 of the precurling punch.

The sides 76 of the die 42 are flat and upwardly diver- In the U-forming operation as shown particularly in FIG. 6, as the composite punch 40 is brought down into contact with the inverted blank 28, initial contact oc-.

curs between the lower edges of the swaging surfaces 68 and the square comer of the underside of the'trailing edge 22 of the blank. As the punch is lowered further, the spaced tongues 30 and the central tongue 32 are bent and the blank is tilted slightly, in a clockwise direction as viewed in FIG. 6, to a position wherein the rounded leading edges 60 of the precurling punch 46 are brought into contact with the inside surfaces of the spaced tongues 30. As the punch continues downwardly past the position of FIG. 6, the spaced tongues 30 are bent about the leading edges 60 of the punch and the rounded trailing edge 62 is brought to bear against the inside surface of the central tongue 32. The precurling of the central tongue 32 proceeds in a manner similar to the precurling of the spaced tongues 30, but slightly delayed with respect to the position of the punch in its downward stroke.

The portions of the spaced tongues 30 precurled in the U-forming operation are immediately adjacent and include a part of the body portion 12 of the blank near the leading edge 16. Thus, the initial bending of the tongues 30 is accompanied by a bending of that part of the body portion from which the tongues extend, as designated by the number 86 in FIG. 6. Because of the ductility of the metal blank, the bending of the part 86 of the body portion takes place without a rupture or tearing of that part from the remainder of the body 12.

, The completion of the precurling of the spaced tongues 30 and the central tongue 32 and the swaging of the leading edge 16 and the trailing edge 22 is accomplished at the bottom of the stroke. As the punch 40 presses the blank 28 to the bottom of the die, the top of the trailing edge 22 is brought into contact with the flat bottom portions and of the curling die and swaging dies, respectively. Further downward movement of the punch causes the blank to be leveled from the tilted position of FIG. 6 and to be further bent and swaged to its final U-formed shape.

Referring specifically to FIGS. 7 and 8, the precurled portions 87 of the spaced tongues 30 are shown formed to the desired shape as pressed between the rounded leading edges 60 of the precurling punch 46 and the leading comers 72 of the precurling die 42, such that the flat outer surfaces of the tongues 30 rest against the side 76 of the die. Similarly, the precurled portion 89 of the central tongue 32 is pressed tightly into the trailing corner 74 of the precurling die by the trailing edge 62 of the precurling punch, the outer surface of the tongue 32 lying flush against the side 76 of the die 42.

Simultaneously with the final precurling of the tongues 30 and 32, the leading edge 16 is swaged to form rounded surfaces 88 conforming to the rounded leading comers 82 of the swaging dies 44; and the bottom of the trailing edge 22 is swaged to form bevels 90 conforming to the swaging surfaces 68 of the swaging punches 48. The rounded swaged surfaces 88 correspond to the outer surfaces of the precurled portions 87 of the spaced tongues 30 such that the entire leading edge of the U-formed blank outwardly from the indented margin 24 is continuously rounded, as best shown in FIGS. 9 and 10. The swaged beveled surfaces 90 are formed so as to extend into and lie coplanar with the knifed bevels 23, such that the trailing an undercut bevel along its entire length.

The swaging of the rounded surfaces 88 of the leading edge 16 causes an extrusion or plastic deformation of the metal. As may be seen by comparing the relative positions of the leading edge 16 with respect tothe leading edge of the swaging punch 48 in FIGS. 6 and 7, the edge 16 is extruded forwardly and substantially compressed. The flat surface portions 64 of the swaging punches 48 maintain the portions of the underside of the link body 12 adjacent the leading edge 16 flat during the swaging of the rounded surfaces 88 such that they remain coplanar with the remainder of the underside 18 of the link body.

The spaced tongues 30 and thecentral tongue 32 of the U-formed blank 28 are curled in a known manner to form, respectively, the spaced knuckles l4 and the central knuckle 20 of the link 10. As described above, the links are interconnected with pins 26 to form a flat top conveyor chain. The chain so formed by links of the present invention is characterized by a close inedge 22 has terfitting of adjacent links. Referring to FIGS. 1 and 2, the trailing edge 22 of each link overlaps slightly the leading edge 16 of the adjacent connected link. Thus, the swaged bevel 90 allows the trailing edge 22 to override the adjacent swaged rounded surface 88, and, in a similar manner, the coplanar knifed bevel 23 overrides the adjacent precurled portion 87 of the spaced knuckle 14. To complete the close interfitting of adjacent links, the knife-formed bevel 25 of the indented margin 24 overlaps the precurled portion 89 of the central knuckle 20. As shown particularly in FIG. 1, a chain comprising links of the present invention has no longitudinal gaps between adjacent links and thereby provides a more nearly continuous conveying surface.

The swaging of the leading edge 16 to provide the rounded surfaces 88 produces a marked increase in the hardness of the metal. The area of increased hardness includes substantially that portion of the link body inwardly from the leading edge 16 to the line of termination of the rounded surfaces 88. In addition and owing to the cold working of the metal associated with the precurling of the spaced tongues 30, the precurled portions 87 of the spaced tongues also exhibit a significant increase in hardness. It is known that work-hardening of a metal produces a corresponding increase in its strength. The contiguity between each swaged surface 88 and the corresponding precurled portion 87 of the curled knuckle provides a hardened, and thus substantially strengthened, area to the portion of the link most susceptible to failure.

In order to attain the desired work-hardening, austenitic stainless steels in the AISI 300 series have been found to be most suitable. In addition to their good cold working qualities, they exhibit extremely good work-hardenability. The results of tests on sample links formed from an austenitic stainless steel in accordance with the method of the present invention show an increase in hardness in the area of the swaged leading edgeof two to two and one-half times that of the stainless steel stock. The corresponding increase in strength has allowed a decrease in the widths of the spaced knuckles l4 and an increase in the width of the central knuckle 20 as compared to prior art links. The net effect is an ability to provide a balanced design link with substantially greater strength without increasing the overall knuckle width, i.e. the distance from outer edge to outer edge of the spaced knucklesl4.

Tests made on comparable stainless steel links of the prior art and links made in accordance with the present invention revealed the following strength increases: in fatigue tests with loads ranging from 12 to 28 percent of ultimate, the improvement in the number of cycles to failure ranged from 67 to 125 percent; in ultimate strength tests, the average load to failure in links of this invention was 122.5 percent of the average load to failure in similar links without swaged leading edges.

Links may be formed by the method of the present invention using metals not having good work-hardening properties. Despite the lessening or. absence of ,increased strength due to increased hardness, links formed of these metals exhibit a relative strength increase over similar prior art links manufactured without the U-forming operation disclosed herein. As explained above, the swaged rounded surfaces 88 form integral extensions of the precurled portions 87 of the spaced knuckles and provide a reinforcing of the knuckles by effectively increasing their widths in the region'where they are subject to the greatest stresses.

Thus, links of the present invention may be made with a low work-hardenable carbon steel, such as AISI 1019. Links formed from plain carbon steel will, of course, not show as great a relative strength increase as those formed from stainless steel. However, its lower hardness and greater ductility provide advantages in increased ease with which it may be cold formed.

There are several variations to the U-forming operation of the preferred embodiment, two of which will be described briefly. First, the knife-formed bevels 23 and 25 (FIG. 3) could be formed by swaging in the U-forrning step. To do this, the precurling punch 46 would be modified to include swaging surfaces adjacent the locators 50 and 54 similar to the surfaces 68 68 of the swaging punches 48. Alternately, the bevels 90 swaged on the trailing edge 22 may be formed independently of the U-forming step. For example, the entire trailing edge may be beveled by knifing in the manner of the knifed bevels 23.

While the invention has been shown and described with particular reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes may be made in form and detail, in addition to those mentioned briefly, without departing from the spirit and scope of the invention.

What is claimed is: 1. In the method of forming a flat top metal conveyor chain link comprising the steps of:

stamping a flat blank from sheet metal, said blank having an intermediate body portion, a pair of spaced tongues extending from one edge of said body portion and a central tongue extending from the opposite edge of said body portion; and

curling said tongues to form cylindrical knuckles adapted to interfit and to be pin-connected with the knuckles of like adjacent links to form a flat top conveyor chain;

the improvement comprising the step of:

U forming said flat blank prior to curling by pressing it into a die such that said tongues are turned downwardly with respect to the flat upper surface of said body portion to form precurled portions of 3. The method as recited in claim'2 wherein said cold said knuckles, and such that said one edge is forming step comprises swaging. swaged to a rounded form corresponding to and 4. The method as recited in claim 3 wherein said U- laterally continuous with the outside surface of the forming step and said cold forming step are performed precurled portions of the pair of spaced tongues 5 Simultaneous extending from said one edge. 5. The method as recited in claim 1 wherein said 2. The method as recited in claim 1 including the Sheet metal steelstep of cold forminganundercut bevel on said opposite The method as melted clfllm 5 Where"! Said edge such that said opposite edge will overlap Said one steel sheet 18 a work-hardenable stainless steel. edge of an adjacent pin-connected link. 10 

1. In the method of forming a flat top metal conveyor chain link comprising the steps of: stamping a flat blank from sheet metal, said blank having an intermediate body portion, a pair of spaced tongues extending from one edge of said body portion and a central tongue extending from the opposite edge of said body portion; and curling said tongues to form cylindrical knuckles adapted to interfit and to be pin-connected with the knuckles of like adjacent links to form a flat top conveyor chain; the improvement comprising the step of: U-forming said flat blank prior to curling by pressing it into a die such that said tongues are turned downwardly with respect to the flat upper surface of said body portion to form precurled portions of said knuckles, and such that said one edge is swaged to a rounDed form corresponding to and laterally continuous with the outside surface of the precurled portions of the pair of spaced tongues extending from said one edge.
 2. The method as recited in claim 1 including the step of cold forming an undercut bevel on said opposite edge such that said opposite edge will overlap said one edge of an adjacent pin-connected link.
 3. The method as recited in claim 2 wherein said cold forming step comprises swaging.
 4. The method as recited in claim 3 wherein said U-forming step and said cold forming step are performed simultaneously.
 5. The method as recited in claim 1 wherein said sheet metal is steel.
 6. The method as recited in claim 5 wherein said steel sheet is a work-hardenable stainless steel. 